Process for damping mineral fibers to be sprayed in air



y 22} 1952 N. L. DOLBEY 2,604,416

PROCESS FOR DAMPING MINERAL FIBERS TO BE SPRAYED IN AIR Filed Sept. 30. 1947 4 Sheets-Sheet 1 42 .1? m. m, l I W l 6i 70 W 1% I 54 64 N. L. DOLBEY July 22, 1952 PROCESS FOR DAMPING MINERAL FIBERS TO BE SPRAYED IN AIR 4 Sheets-Sheet 2 Filed Sept. 50. 1947 F/GZ.

Attorney N. L. DOLBEY July 22, 1952 PROCESS FOR DAMPING MINERAL FIBERS TO BE SPRAYED IN AIR 4 Sheets-Sheet 5 Filed Sept. 30, 1947 FIGS. 3 46 42 40 2 73 July 22, 1952 N. DOLBEY 2,604,416

PROCESS FOR DAMPING MINERAL FIBERS TO BE SPRAYED IN AIR Filed Sept. 50, 1947 4 Sheets-sheaf. 4

Attorney.

Patented July 22, 1952 PROCESSFO *DAMP ING' FIBERS" g TOIBE SPRAYEn-INAIR N rm nh Dqlb ngA a. i d iEn a di sv signor to J Roberts Limited; Armley, Leeds; nng anaa British company v w 30, 1947, Serial N01 776 .964

' 5 mmnib-n September 4 Claims. (01. iii-1'00) vemefiective way of forming insulating coatings: on walls; ceilings orother surfaces is tospray asbestos-fibre with ,orwithout other ma teri'aland-with'an-adhe'sive or ingredients which reaotzto form an adhesive.

:Dhis processcanadvantageously: be carried out in-thef manner and'witl i' the vapparatus described in" United States, Patents Nos; 1,990,584 and 1 -;990,585issuedtome on- February 12, 1935,-the fibrebeing. suspended inair and then subjected to-suotionbut when -this isdone there is one practical drawback. This drawback is that dust escapes into the atmosphere during the sprayingoperatiomand; in order to overcome it; many expedients have been-tried; The drawback can be overcome by the method described in my United- States application Serial No. 603,616, July 7411945, Patent No; 2,563,457 issued August '7; 1-95l-,=-t hatis'tosay, by mixing. the asbestos with apredetermmed=quantity of water or other dampingmaterial such a way that in the course: of-the mixing substantially every particle 01; asbestosis damped and the damping material'is' -so uniform-1y,- distributed-throughout the asbestos that-thereis no-tendency for particles to-sticlt together by reason of different moisture contents. In my; saidapplication No. 603,616 I have alsodescribed; apparatus by which this process-can=be; carried out,- this'apparatus in-.

corporating-lamotarymixing drum ada-pted to carry the asbes es upwardseas thedr-um rotates and a rotary brush mountedwithin the'drum to engage the asbestos" which is carried upwards and by abeating action to open up fibre bundles andfii-ngthe particles-through the drum to-falltothe bottom' and be carried upwards again.

Such; an; apparatus serves totreat batches of asbestosrfibrer Nowit is desirable to-be able to work' continuously that is to say; to feed dry asbesto -to an amiaratus such'as that 'shown in niwfatents Nos. 13196584 and 1,990,535 and to spray'it-without having. to damp the fibre-in batches. A n Qbjector this invention is to enable" asbestos-or other mineral fibre-e g.- glass fibre,

tube 4 supplied-in a current of air to a spraying device substaritia-lly-freeof dryand loosedust.

Anotherobiectof theinvention is to provideimprovedmeans fordamping-asbestos or other fibresr; a result of many researches; I havewill: fibres withwaterLor other damping:

'2 agent while itis travelling in a i thin layer and"- before itis suspended in air,-Icontrol-thedamp; ing in accordancewith the flow of fibre, and feeding the damped fibreparticles'into th'e air current I prevent suction I being; exerted to any: substantial extent. on such dust as is formed-see; that; practically no such; dust-is drawn into -the* air'current. i H I It; is important thatthe damping should-be as. uniform (as-possible andior thisreason the fibreshould be; spreadout into-a thin -layer,;; that-isto say. one; thinner than is usual" at the present time; The dampin agent sprayed onto; this-- layer ma be water in atomised form, oil u-any appropriate liquid. It is; simplestto use water, and thewater jetshould Joe as fine as possible. Inaddition to damping the thin layer offibre; such a -jet also creates-afog-like atmosphere; which-tends to cause any dust'formed to settle w th n apn a A .7 o, V I prefer to effect-thedamping in a casing; through which the thin layer travels and which is substantially closedrandit is an important feature that the interior 'fof thiscasingis not; in communication with any space under low pres-- sure such that dust in-suspensioninthe casing would be-drawn out of it by suction p In' carryingout the processv I prefer-to e ploy an apparatus such as that shown in my Patents; Nos. 1,990,584and 13990585 with a conveyorbelt to carry the fibrefupwards past a brush whichg serves to -remove all 'thefibre except the desired thin layer and to modify this apparatus bypro viding means forsprayingatomised water onto the thin layer while it isstill on theconveyor belt, the layer being nemoved; from the-bel't-by a stripping brush, The thinner the layer of fibre which is sprayed with the water'the betterg theresults as the fibre and water b'ecomemore uniformly mixed. It-is-possibleto make the-layer thinner withoutreducingthecapacity of a given apparatus by increasing the speedxof the con veyor and making: thefirst brushapproach'the conveyor closely.- I find it-imposs-ible toflamp? the fibreabsolutely uniformly while it is' on'; the conveyor; andaccordingly a little-dust -isproduced-E by the action of thestripping brush and-cone veyed;t o the spraying-device. However; thisdust is-,rel;atively smalL-in amount and to ,keep itatofi a: minimum-the 'speed'qoi the stripping brush should-be madeas: low aspossibleh 1 In the apparatus described in' my PatentstNosi particles-are proj ectedis drawniintocthessuctiorr inlet of a fan,-- so-in-efiect=-the particlesaform a 3 o suspension in a moving current of air and this suspension is conveyed forward by the fan. In

'drum'forms the upper roller for an endless belt that apparatus it is the fan which produces the greatest part of the dust. In the present invention I may still use a fan but by the time the fibre arrives at the fan it is already suificiently damped to prevent any appreciableformation of further dust in the fan.

So far as possible, no dust should be drawn forward with the fibreand, to this end, I prefer to modify the apparatus further. In'the first place, when I employ a fan to convey the suspension forwards, I prefer to cause the fan to draw in air from the atmosphere so that the suction which it produces is not exerted to any substantial extent upon the interior of the casing. This result is preferably attained by splitting into two parts a duct through which the fibre conveyor H, which also passes over a roller I2 carried in bearings i3 supported by the members 6 and 6. The conveyor H is driven by an electric motor l5 mounted on the base members I,

' of a gear 2| of the epicyclic type, which is itself secured to anotherannular plate 22 fixed inside the drum. The gear 2| connects the shaft 3 falls from the stripping brush, the upper end of I the lower part surrounding and overlapping the lowerend of the upper part so as'to leave a space through which air can be drawn in from the surrounding dust-free atmosphere.

Instead of 'causing' the particles to pass through a'fan I may entrain them in an air current which may itself be producedby a fan. For instance, the particles on being projected into air by a stripping brush may fall down a funnel-like duct to a continuously rotating valve of the star or gate type, throughwhich the particles pass into a pipe in which the-air current is flowing. Such a valve serves to break any suction which would otherwise be applied to the interior of the casing. I

As stated above, the spraying of the damping agent must be controlled in synchronism with the movement of the fibre. -In existing apparatus for spraying asbestos fibre, it is usual to provide a pneumatically operated clutch for the conveyor belt and to operate this by'a device fixed to the spraying nozzle so that the. belt is stopped whenever spraying. is stopped." In the present invention the spray of atomised water, oilor other damping agent may be stopped simultaneously under the same control.

- The preferred form of apparatus according to the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a somewhat diagrammatic tion of the apparatus, partly, in section;

Figure 2 is a section on the line IIII'in Figurel;

"Figure 3 is a central vertical section through the part of the apparatus shown in the upper right-hand part of Figure 1; a

Figure- 4 is an enlarged section-on the line IV-IVin Figures; and V 7 Figure 5 is a perspective-view of interior of the apparatus; and

Figure 6 is a diagrammatic view of the mechanism for controlling the damping.

The apparatus is carried by an angle-iron elevapart of the V framework having two side frames each com+ members 5, 3 and 4. The two side frames are united by cross-members (not shown) at the base and top. The space at each side between the'members 2,.3, 5 and! is closed by cheek plates 8 and 9,-tne plate 8 at each side being of sheet metal and the plateISbeing a casting which serves as a main bearing for a drum Ill.

The

and a shaft 23 to. which a wheel 24 is keyed.

This wheel has a series of holes 25 around its periphery and these can be engaged by a plunger 26 mounted to slide in 'a cylinder 2'! fixed to the side of the apparatus.

drawal of the plunger 26 from the hole 25, the' frictional resistance of the drum lfl and con 9 veyor ll causes the gear to drivethe shaft 23 preferentially and the drum and conveyor stop. Above'the conveyor ll there is a sheet metal hopper 2B which is kept charged with asbestos fibres and has a lid 3! hinged at 32 to a fixed cross-piece 33. conveyor there is a sheet metal plate 33 which Beneath the lower run of the spans the two side members 3. a

The central part of the conveyor II carries a series of spikes 34 and on each side of these the belt is smooth and projects laterally beyond the hopper 28, so that in effect the bottom of the hopper is formed by the spiked part ofthe eonveyor. 34 pick up asbestos and carry'it upwardsa It is important that only'a thin uniform layer'of asbestos should remain on the conveyor at the top of the upward run, and a brush 35 is provided to sweep over the conveyor and detach and re turn to the hopper any asbestos in excess of this- This brush is carried in bearings thin layer. which are fixed to the frame members' zythe shaft of the brush passing'through bushings in the side walls of the hopper.

The thin uniform layer of asbestos which-is left on the-conveyor by thebrush 35 passes be neath a plate 40 which spans the interior ofthe hopper 28 and forms'one wall of-a damping the walls of the hopper 28 and joined tothem-by- The chamber M is thus wider curved Walls 58. than the hopper 28 and in fact it is nearly the fullwidth of the belt I l. Alongthe'walls 53'th e side members 2 are madenarrowerfas showni in Figure 4, and the walls of the hopper 28 and-53 are united by cross parts 54! which stop short of the smooth edge surfaces of the conveyor II. The result is to form openings 59 at each side of the chamber 4|, these-openings leading" onto the members 2 outsidethe-hopper 28. The top of the chamber 4! is constituted by a lid hinged at-43 to the cross-piece 33." a

i In the dampingchamber il-there isa spray nozzle 4'4 held between semi-circular parts 45' of When the plunger enters" one 'of the holes 25 the shaft 23 cannot rotate;'

When the conveyor is running thespikesthe si de" walls of the 9 chamber 41-. nozzle 4451s red withwater through a pipe 4-"Iand 'W-ithcompressed air -through -a-' pipe 48'; It. includes;

an orifice=49 which can be closed by an'eedle' valve water flowing to the orifice from the pipe 41.

The nozzle then delivers an atomis'ed fan shaped 'spray of water which when it strikes theconveyor is of the same-width as the part covered bythe spikes 34; Theamount o'ffl'wat'er may, for

examplegbe-from 5 to I by weight of the asbestos. The spray camps "the asbestos substan-= tially-uniformly and producesa. moist atmospherein the damping chambrf l'li As theconveyor 'beginsits downward run the asbestos is removed by a stripping brush 60 which is mounted on a shaft 51 carried in bearing brackets 62 which are fixed to the vframe members I. This shaft 6| is driven by a belt 64 from the shaft l8 and in turn it drives the shaft of the brush 35 through a belt 65.

Thelbrush 60 works in, and in effect constitutes a' wall of, a chamber in having sidewalls 1| aligned with theside Walls of the hoppe'r 29 and secured to the members 1-. This chamben'lli-is closed by a" 0ll1V6d."1ld"12' hinged at 13' and it is narrower than thechamber'4'luWhere the two chambers meet there'is a cross-plate 14 which stops short of the smooth edges of the conveyor and leaves opening-s 15 through which any'material on the smooth edges can pass.

The chamber 10 in turn merges into the top of a chute 16 into which the particles of asbestos detached by the brush 60 fall. This chute has side walls 11 which overlap the lower part of the brush 60, a wall 18 which nearly touches the spikes 34 on the conveyor II and a wall I9 which extends far enough upwards to form an abutment for the lower edge of the lid 12.

The chute 16 is continued as the first half 80 of a two-part duct, the second part of which, 8|, has an outlet registering with the suction inlet of a fan 82 mounted to rotate about a horizontal axis. This fan is driven through a belt 8'3 by the motor |5. Itv receives the particles of asbestos which fall down the duct and delivers them through a pipe 84 to a spraying device 85. From this device the asbestos is sprayed at the same time as an emulsion of rubber in water which is supplied to the device through a pipe 86, the asbestos and emulsion being projected onto a wall or other surface to be coated. The emulsion is sprayed and atomised under the action of compressed air delivered through a pipe 81 and it acts as an adhesive for the asbestos.

It will be observed that the lower end of .the part 80 of the duct lies wholly within the mouth of the part 8|, which is itself surrounded by a hood 90 so as to leave an annular opening 9| through which the air can be drawn in. By using such a broken duct the suction exerted by the fan is applied substantially entirely to the atmospheric air through the opening 9|.

It will be seen that in the apparatus shown the asbestos travels through a substantially closed casing which is divided into (or constituted by) the hopper and the chambers 4| and 10. It is inevitable that some dust will be formed within this casing, if only because of the high speed at which the brush 35 mus-t rotate and the consee I quent fan-like efiect it produces. The. purpose of the invention is to reduce to' a minimu'm the amount of dust delivered to the spraying'device 85, and the-apparatus-shown in Figure 1' can if necessary be put where dust escaping from i t fis the atmosphere: in the-chamber it is harmless. Once it -ha's-'-b'e'-- come damp enough to 'fall o'utof the suspension i it is" no longer har'mful' 'dustbutrather'damp particles of asbestos which can-beallowed'tb f all to'the ground to be swept up later if" they pass out't'hrough theopenings '59- or -'|5-.' The la yen of asbestos is not liftedfromthe conveyor until= it has been damped,- s'o'only little dust is-prmduced'" by the-stripping'brush 60*. As the part'i o'f '-the-chamber-10 below'thebrush Ellis not under:

low pressure, thereis no" tendency for dust to be drawn in and past the brush 69 from any part of the interior of the casing by suction-fi' Insteadthe brush merely detaches damp fibre from the conveyor and conveys onwards damp p'artic'les which are alreadyfallingiii-the upper part'of-the chamber-1D and which, because they-a falling. are not harmful dust; I e

The compressed air supplied to the nozzle: 44 is small involume. It" is supplied u'ndera pressure of, sayBO'lbs. per squareinch and-it sets up very littlepressure in "the damping chamber 41'. Even this pressure is largely relieved beneath the loweredge of the plated-9; and theturbulence the clots become overwetted they fall onto the smooth edges of the belt II and roll back down these smooth edges and out through the openings 59.

Thus it will be seen that the interior of the casing is substantially closed and not subjected to suction, so that very little dust escapes from it and the fibre conveyed to the spraying device is substantially dust-free.

The operator controls the whole operation through a single operating handle which is connected to a double valve which controls the flow in both the pipes 86 and 81. A pipe 96 branches from the pipe 86 and runs to the cylinder 21. This contains a piston 98 which is moved against a spring 99 when air is allowed to flow in the pipe 96 and which carries the plunger 26. As a result, whenever the handle 95 is turned to stop the spraying of the asbestos the plunger 26 is withdrawn, the wheel 24 turns and the belt is stopped.

The pipe 48 runs from the cylinder 21 to the nozzle 44, and whenever the conveyor is stopped the supply of air to the nozzle 44 is also stopped. The water spray is then stopped because the diaphrag-m 5| moves the needle valve 59 to close the orifice 49.

continuously by moving the surface, dampening said fibers with an atomized liquid as the layer advances, substantially separating the dampened fibers from each other as the layer advances and simultaneously scattering-said separated fibers into the upper part of an enclosed air space which is opened at its lower end and which has intermediate its upper and lower ends a restricted opening to the atmosphere, establishing a downwardly flowing current of air in the lower. part of said air space by creating a; partial vacuum at the lower end thereof, whereby as said separated fibers fall through the upper part of said air space and into the flowing current of'air in the lower part of the air space they are forcibly delivered by said current of air into thefhigh velocity air stream of the spraying device. I

2. A process as set forth in claim 1 and in which the mineral fibers are asbestos.

3. In- 'a process for delivering loose mineral fibers to a spraying device having a high velocity air stream, the steps of arranging the mineral fibers into a relatively thin, fiat layer on a movable supporting surface which leads into the top of an enclosed air space which is open at its lower end and has a restricted air inlet intermediate its upper and lower ends, advancing said layer progressively into said air space by moving said surface, dampening said fibers while on said surface with an atomized liquid as said surface advances, substantially separating the dampened.

fibers from each other as they are received into Said air-space and simultaneouslyscattering and projecting said separated fibers in the upper part of said air space,,establishing a currentof air flowing; downwardly from said intermediate air inlet tothe open lower end of said air space by creating a partial vacuum at said lower" end, whereby as said separated fibers fall through the upper part of said air space andinto the flowing current of air in the lower part of said air space the fibers are forcibly delivered by said current of air into the high velocity air stream of the spraying device. a a

4. A process as set forth in claim 3 and which includes the step of maintaining said partial vacuum at the lower end of said airspace of such.

low intensity that substantially no air or dust is drawn from that part of the enclosed air space which is above said intermediate air inlet.

I NORMAN L. DOLBEY.

REFERENCES ci'rnp V The following references are of record in the file'of this patent:

UNITED STATES PATENTS 

1. IN A PROCESS FOR DELIVERING LOOSE MINERAL FIBERS TO A SPRAYING DEVICE HAVING A HIGH VELOCITY AIR STREAM, THE STEPS OF ARRANGING THE MINERAL FIBERS INTO A RELATIVELY THIN, FALT LAYER ON A MOVABLE SUPPORTING SURFACE, ADVANCING SAID LAYER CONTINUOUSLY BY MOVING THE SURFACE, DAMPENING SAID FIBERS WITH AN ATOMIZED LIQUID AS THE LAYER ADVANCES, SUBSTANTIALLY SEPARATING THE DAMPENED FIBERS FROM EACH OTHER AS THE LAYER ADVANCES AND SIMULTANEOUSLY SCATTERING SAID SEPARATED FIBERS INTO THE UPPER PART OF AN ENCLOSED AIR SPACE WHICH IS OPENED AT ITS LOWER END AND WHICH HAS INTERMEDIATE ITS UPPER AND LOWER ENDS A RESTRICTED OPENING TO THE ATMOSPHERE, ESTABLISHING A DOWNWARDLY FLOWING CURRENT OF AIR IN THE LOWER PART OF SAID AIR SPACE BY CREATING A PARTIAL VACUUM AT THE LOWER END THEREOF, WHEREBY AS SAID SEPARATED FIBERS FALL THROUGH THE UPPER PART OF SAID AIR SPACE AND INTO THE FLOWING CURRENT OF AIR IN THE LOWER PART OF THE AIR SPACE THEY ARE FORCIBLY DELIVERED BY SAID CURRENT OF AIR INTO THE HIGH VELOCITY AIR STREAM OF THE SPRAYING DEVICE. 